This invention relates to an automatic gear change control apparatus for an automobile and a method of controlling such apparatus, and more particularly to an automatic gear change control apparatus capable of reducing a shock (jolt) due to a gear change (gear shift) and a method of controlling such apparatus.
It is already known, for example, from Japanese Unexamined Patent Publication No. 56-39925 (corresponding to U.S. Pat. No. 4,403,527) to control the output of an engine during a gear change of a transmission in order to reduce a shock occurring at the time of the gear change such as gear shift-up or shift-down. Such methods of controlling the engine output are mostly either to control the opening and closing of a throttle valve or to control a valve opening-time of a fuel injector valve or an ignition timing.
Japanese Unexamined Patent Publication No. 55-69738 (corresponding to U.S. Pat. No. 4,266,447) discloses an automatic gear change control apparatus in which a jolt (gear-change shock) control-starting speed (nlnA) and a terminating speed (nlnE) are calculated from the rotational speed of the engine obtained when starting the gear shifting, and the output torque is controlled during a period when the rotational speed of the engine actually changes from the speed nlnA to the speed nlnE.
However, in the above conventional automatic gear change control apparatuses, although it is possible to reduce the engine output particularly when shifting up the gear, it is not possible to abruptly emit the rotational energy so far stored. Actually, it is difficult to lower the rotational speed of the engine to a required level in a short time period of the gear shifting, particularly at the time of gear shifting-up during acceleration. Namely, in the above prior art, although it is necessary to reduce a difference between the rotational speeds of the opposite sides of a clutch in order to reduce a gear-change shock in the automatic transmission, a braking force is not positively applied to the engine, and it is difficult to lower the engine rotational speed to the target speed in a short time. Therefore, the above prior art has a problem that it is impossible to sufficiently suppress the gear-change shock.